In any classroom, at any moment, a few students may be trying to follow you.

"It's...complicated. And we need to move on" kills inquiry, kills science, but apparently not science education.

When you present a model in class, make it clear it's a model. Science teachers are, essentially, model makers.

I'd rather children come out of school knowing nothing than "knowing" science. A child who knows nothing may still be curious.

A child who "knows" science has been functionally lobotomized.

***

When I was young, I was taught that the sun was directly overhead at noon. I remember trying to test this. I pushed a stick into the ground, expecting to see the shadow disappear at noon. It never did.

I did this over and over and over again. It never occurred to me the teacher was wrong.

Many children come to school in this neck of the woods still believing in Santa Claus, the Tooth Fairy, and the Easter Bunny. Many leave 12 years later believing in astrology, the moon landing hoax story, and false ancient Mayan prophecies of world destruction.

Few can explain seasons or tides or evolution. Many adults who think they grasp these don't. Discussing descent with modification with Creationists can be frustrating, but hearing those who "believe in evolution" toss around fallacy after fallacy is infuriating. I'm not sure which group does more harm to science education.

If you do not have a good grasp of a concept, do not attempt to teach it.

To earn a license to teach biology in New Jersey, you need to score a 152 (on a 200 point scale) on the biology Praxis test. In Arkansas, a 139 gets you in. Both scores are far below the 179 needed to earn the Praxis Series Recognition of Excellence.

There are, of course, other ways to measure teacher effectiveness, and knowing something doesn't mean you can competently teach it.

Not knowing something, though, means you can't teach it.

No one, of course, knows everything. I'm not arguing that we need to raise the Praxis passing score to 190.
Just know your limitations. If you don't grasp a point, don't pretend you do.

Randall Munroe is, of course, the xkcd guy.
He should be mandatory reading for science teachers.